Rochester secondaries not opening
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,160
Likes: 23
From: Prescott AZ
Rochester secondaries not opening
I have a 1970 with a 350hp 350, rochester carb and close ratio 4 speed. It was hard starting when cold when I got it. The choke worked properly but what I found was that the accelerator pump was not shooting gas into the carb when I would step on the throttle. After warming up it ran great and the secondaries opened fine. So I took the carb off and disassembled it, cleaned it, put a rebuild kit in with new pump and reinstalled. It now starts and runs great but I can't seem to get the secondaries to open from inside the car via the gas pedal. They will open when I throttle it from under the hood. I'm sure it's just an adjustment but have't had much luck figuring it out. I would appreciate any help/ advise you guys can offer.
Thanks,
Rob
Thanks,
Rob
Race Director
Joined: Sep 2002
Posts: 10,362
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From: San Diego - Deep Within The State of CONFUSION!
Melting Slicks
Joined: May 2006
Posts: 2,590
Likes: 403
From: Nashville TN
St. Jude Donor '09
This sounds like your problem. Will open manually from carb, but won't open when pressing pedal. Reach down and grab pedal and pull it up, slightly bending pedal link. I have to do this occassionallyon mine. Also, as previously mentioned, make sure choke is opening up 100%, if not, it will lock out the secondaries from opening. Mine is a mother to start and I have been putting off rebuild. I guess I'm going to have to bite the bullet and do for the same reason . . . accelerator pump is shot.
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
Since you can operate the 2nds from the throttle lever, I'd check the cable first.Here's the 207 cable view. Make sure you adjust the cable to the bracket properly, and that the bracket's "nub" seats in the carb base.
207 choke side....
207 choke side....
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,160
Likes: 23
From: Prescott AZ
Thanks for the input guys. I do know that it has to be fully warmed up so that the secondaries can open. That is not the problem. Sounds like the linkage may need to be checked. I will do that this weekend.
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Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
No Q-Jet pro, but worked on several, and learned a few thing's. A well tuned Q-Jet will wamp any other other design on the street, but don't like to be field serviced. You mentioned secondary throttle plate problem's on your's, but can be the lower mechanical main's, or upper vacuum controlled plate's. As mentioned, there's several lock out's for the bottom main's, but sometime's over torquing the upper body screw's can hang up the vacuum plates. A slight filing usually correct's this, and good to check secondary enrichment power piston action while you're at it.
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
In reading your posts, it seems this started after the rebuild. I'd suggests looking at the choke linkage. As has been mentioned already, there are several "lock outs", but the one that's usually adjusted incorrectly that causes the issue you're having is the small tang from the choke that keeps the secondaries opening until the choke is opened enough. You can see it in the second pic Dennis posted. It's the small piece that keeps the pin coming off the secondary shaft from allowing the secondaries to open. To correct/verify this is adjusted correctly, do a search for Lar's article on adjusting the choke properly. It's the best write up I've seen and works perfectly.
Thread Starter
Burning Brakes
Joined: Oct 2010
Posts: 1,160
Likes: 23
From: Prescott AZ
This sounds like your problem. Will open manually from carb, but won't open when pressing pedal. Reach down and grab pedal and pull it up, slightly bending pedal link. I have to do this occassionallyon mine. Also, as previously mentioned, make sure choke is opening up 100%, if not, it will lock out the secondaries from opening. Mine is a mother to start and I have been putting off rebuild. I guess I'm going to have to bite the bullet and do for the same reason . . . accelerator pump is shot.
Rob
